Mn、Co掺杂ZnO薄膜结构及发光特性研究

利用脉冲激光沉积(PLD)方法在Si(100)衬底上制备了ZnO、Zn0.8Mn0.2O、Zn0.8Co0.2O薄膜.薄膜的晶体结构和表面形貌采用X射线衍射仪和原子力显微镜测试.表明薄膜具有明显的c轴择优生长取向,薄膜表面较为平整,颗粒尺寸在纳米量级,薄膜中晶粒的生长模式为"柱状"模式.此外,Mn、Co掺入后,薄膜的X射线衍射峰有小角度偏移,这与 Mn2 、Co2 离子半径有关.PL谱显示Mn、Co掺杂ZnO薄膜的蓝、绿发光峰的位置相对纯的ZnO薄膜没有改变,还出现了紫外发光峰,其中Mn掺杂的蓝、绿光峰的强度减弱,Co掺杂的蓝光峰强度减弱,绿光峰强度增强.这是因为Mn、Co掺入改变了ZnO本征缺陷的浓度,发光峰的强度也随之而改变.     

氧氩比对磁控溅射ZnO薄膜结构及光致发光性能的影响

采用射频反应磁控溅射法以不同的氧氩比在玻璃衬底上制备了ZnO薄膜,并对薄膜进行了退火处理;利用X射线衍射仪（XRD）和原子力显微镜（AFM）分别对薄膜的物相组成和表面形貌进行了分析,利用荧光分光光度计对ZnO薄膜的室温光致发光（PL）谱进行了测试。结果表明：当氧氩气体积比为7∶5时,所制备的ZnO薄膜晶粒细小均匀,薄膜结晶质量最好;ZnO薄膜具有紫光、蓝光和绿光三个发光峰,随着氧氩比的增加,蓝光的发射强度增强,而紫光和绿光的发射强度先增强后减弱,当氧氩气体积比为7∶5时紫光和绿光的发射强度最强。     

磁控溅射MgxZn1-xO薄膜的结构与光学性能研究

利用射频磁控溅射技术在玻璃衬底上沉积了MgxZn1-xO(x=0～0.2)薄膜.采用X射线衍射仪、紫外-可见光分光光度计和荧光光谱仪研究了Mg掺杂量对MgxZn1-xO薄膜结构与光学性能的影响.XRD图谱表明,MgxZn1-xO薄膜均为六角纤锌矿结构,并且呈现出C轴择优生长特性,当x>0.1时薄膜出现(100)面衍射峰,薄膜的c轴择优生长特性减弱,随着x值的增加,晶格常数c逐渐减小.紫外可见光透射光谱表明,Mg的掺入提高了薄膜在可见光范围内的透过率,同时使薄膜的禁带宽度增大.PL谱分析显示,Mg的掺入使薄膜的紫外发射峰和蓝光发射带发生蓝移,当x=0.1时近带边发射峰与杂质发射的强度比值最高.     

Co掺杂量对ZnO薄膜结构及光学特性的影响

采用脉冲激光沉积法(PLD)在SiO2村底上成功制备了具有c轴择优生长特性的Zn1-xCoxO(x=0.05、0.1、0.2、0.3)系列薄膜.通过X射线衍射和能谱仪研究了Co掺杂量对薄膜晶体结构和成分的影响;同时利用光致发光谱(PL)和透过率研究了薄膜的光学特性.结果表明,当掺杂浓度为10%时,薄膜生长最好,c轴择优生长最为显著;Co元素的掺入改变了薄膜的紫外、绿光和蓝光发射,分析认为主要是Co元素的掺入量改变了薄膜的禁带宽度、氧错位缺陷浓度和锌填隙缺陷的浓度;Co元素掺杂浓度为5%时,薄膜的透过率超过90%.此外,探讨了不同波段光发射的可能机理.     

衬底温度对Mg0.1Zn0.9O薄膜结构及光学性能的影响

利用射频磁控溅射技术在不同温度的(100)Si和玻璃衬底上成功地制备了c轴择优取向的Mg0.1Zn0.9O薄膜.通过X射线衍射(XRD)、场发射扫描电镜(FESEM)、紫外可见光分光光度计和光致发光谱研究了衬底温度对Mg0.1Zn0.9O薄膜结构、表面形貌和光学性能的影响,结果表明,在衬底温度为400℃时生长的Mg0.1Zn0.9O薄膜具有很好的c轴取向和较好的光学性能.用激发波长为300nm的氙灯作为激发光源得到不同衬底温度下Mg0.1Zn0.9O薄膜的室温PL谱.分析表明,紫外发光峰与薄膜的结晶质量密切相关,蓝光发射与氧空位有关.简单探讨了衬底温度影响紫外光致发光峰红移和蓝移的可能机理.     

Mg-Al共掺杂ZnO薄膜的制备及其光学特性

采用溶胶-凝胶（sol—gel）旋涂法在载玻片上制备了不同A1掺杂量的Mg—Al共掺杂ZnO薄膜．在室温下利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和光致发光（PL）谱仪等手段分析了Mg—Al共掺杂Zn0薄膜的微结构、形貌和发光特性．XRD结果表明Mg．AI＆掺杂zn0薄膜具有六角纤锌矿结构;随着Al掺杂量的增加,共掺杂薄膜呈C轴取向生长．由SEM照片可知薄膜表面形貌随Al掺杂量的增加由颗粒状结构向纳米棒状结构转变．透射光谱表明共掺杂薄膜在可见光区内的透射率大于50％,紫外吸收边发生蓝移．在室温下的PL谱表明Mg—Al共掺杂zn0薄膜的紫外发射峰向短波长方向移动：Al掺杂摩尔分数为1％和3％的Mg—Al共掺杂ZnO薄膜的可见发射峰分别为596nm的黄光和565nm的绿光．黄光主要与氧间隙有关,而绿光主要与氧空位有关．     

衬底温度对PLD方法生长的ZnO薄膜结构和发光特性的影响

在不同的衬底温度下, 通过脉冲激光淀积的方法在Si衬底上生长出c轴高度取向的ZnO薄膜. ZnO薄膜的结构和表面形貌通过X射线衍射和原子力显微镜表征. 同时以He-Cd激光和同步辐射作为激发源来测试样品的发光特性. 实验结果表明, 在衬底温度为500℃时生长的ZnO薄膜具有非常好的晶体质量, 并且表现出很强的紫外发射. 在用同步辐射为激发源的低温(18K)光致发光谱中, 还观察到了一个位于430nm处的紫光发射, 我们认为这个紫光发射与存在于晶粒间界的界面势阱所引起的缺陷态有关, 这个势阱可能起源于Zn填隙(Zn _i)     

脉冲激光沉积ZnO薄膜的制备及其性能研究

本文用脉冲激光沉积(PLD)法在SiO2基片上制备了ZnO薄膜和Zn1-xMnxO薄膜.X射线衍射、原子力显微镜、紫外-可见光分光光度计对ZnO薄膜的测试结果表明:薄膜具有(103)面的择优取向,表面比较平坦;SiO2基片上制备的薄膜在387 nm附近存在明显的吸收边,且薄膜的吸收对基片温度变化不明显.通过对Zn1-xMnxO薄膜的吸收光谱分析得出:Mn离子的掺杂改变了ZnO薄膜的禁带宽度,随着Mn离子掺杂量的增加,薄膜禁带宽度增加;薄膜的光吸收也从直接跃迁过渡为间接跃迁.     

RF溅射稀土掺杂ZnO薄膜的结构与发光特性

通过射频磁控溅射技术在Si(111)衬底上制备了未掺杂和La、Nd掺杂ZnO薄膜.XRD分析表明,ZnO薄膜具有c轴择优生长,La、Nd掺杂ZnO薄膜为纳米多晶薄膜.AFM观测,La、Nd掺杂ZnO薄膜表面形貌较为粗糙.从薄膜的室温光致光谱中看到,所有薄膜都出现了395 nm的强紫光峰和495 nm的弱绿光峰,La掺杂ZnO薄膜的峰强度增大,Nd掺杂ZnO薄膜的峰强度减弱,分析了掺杂引起PL峰强度变化的原因.     

退火温度与Tb掺杂对六角锥形氧化锌发光性能的影响

采用燃烧合成法制备了六角锥形氧化锌（ZnO）粉体,利用X射线衍射谱（XRD）、扫描电子显微镜（SEM）和光致发光谱（PL）研究了退火温度与Tb掺杂对ZnO粉体形貌结构和光学性能的影响,实验结果表明,600℃退火得到的晶粒六棱锥形最明显;不同退火温度处理后的样品光致发光谱都有紫光、蓝光和黄光;升高退火温度,样品结晶程度和发光强度提高,黄光发生蓝移;Tb掺杂使材料出现蓝移现象,并在546nm处出现了绿光发射峰。     

Structural, optical and photoluminescence studies of heavily Mn-doped ZnO nanoparticles annealed under Ar atmosphere

Undoped and heavily Mn-doped with ZnO nanoparticles (Zn_1?xMn_xO, x?=?0.0, 0.05, 0.1 and 0.2) annealed under Ar atmosphere have been synthesized by a sol–gel method. The structural properties and optical absorption of the prepared samples have been examined by powder X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared (FTIR) spectroscopy and UV–visible spectrophotometer. Hexagonal wurtzite structure of the samples is confirmed by the XRD spectra. The average crystalline size of the Zn_1?xMn_xO nanoparticles has been calculated from X-ray line broadening and is decreased from 35.73 to 18.24?nm with increase in Mn concentrations from 0.0 to 0.2. The increase in lattice parameters indicates the substitution of Mn in ZnO lattice. SEM and TEM photographs indicated that the grain size of undoped ZnO is bigger than the Mn-doped ZnO which is due to the limitations of grain growth upon Mn doping. The presence of functional groups and the chemical bonding due to Mn doping is confirmed by FTIR spectra. PL spectra of the Zn_1?xMn_xO system showed that the shift in near band edge emission at 390?nm and a blue band emission at 450–490?nm which confirms the substitution of Mn.     

Optical and magnetic properties of Mn doped ZnO samples prepared by solid state route

The structural, optical and magnetic properties of Zn_1?xMn_xO (x = 0.02, 0.04 and 0.06) prepared by solid state route are presented. The rietveld refined X-ray data revealed single hexagonal phase with the space group P63mc in all samples. Significant blue shift with Mn doping is observed in UV–Visible studies, supported by photoluminescence spectra showing a high intensity UV emission peak followed by the low intensity green emission band corresponding to oxygen vacancies and defects. Photoluminescence spectra also suggested that doping of Mn can affect defects and oxygen vacancies in ZnO and giving the possibility of band gap tuning for potential applications in optoelectronic devices. All single-phase samples exhibit paramagnetic behaviour at room temperature, involving small proportion of defect mediated ferromagnetic ordering.     

Role of additives; sodium dodecyl sulphate and manganese chloride on morphology of Zn1−xMnxO nanoparticles and their photoluminescence properties

In the present study Zn_1−xMn_xO (x = 0, 0.05 and 0.1) nanoparticles (NPs) have been synthesised in aqueous solution phase at mild reaction temperature 100 °C in moderate alkaline medium (pH = 9.5), and the role of external additives; like sodium dodecyl sulphate and manganese chloride on the morphology and size of the products has been explored on the basis of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectral analyses data. ZnO hexagonal nano-plates, core–shell like spherical/ellipsoidal Zn_0.95Mn_0.05O structures and thin sheets, thorn/needle mixed shaped Zn_0.9Mn_0.1O structures have been observed in TEM and SEM images. Zn(OH)₂ formed in moderate alkaline medium, converted to Zn(II) hydroxo complex ions on dissolution, which further recrystallizes to produce wurtzite ZnO at 100 °C. From XRD and EDX analysis, successful doping of Mn²⁺ ions at the Zn²⁺ sites in ZnO host has been proved. In the photoluminescence spectra, the observed blue shifts in NBE peaks and decrease of emissions intensity on Mn doping have thoroughly been discussed in the present investigation.     

A study of structural, optical and magnetic properties of Cr, Ce co-doping in ZnO diluted magnetic semiconductors

We present the structural, optical and magnetic properties of pure ZnO, Zn_0.97Cr_0.03O and Zn_0.96Cr_0.03Ce_0.01O samples, the samples were synthesized by sol–gel method. The microstructures, optical and magnetic properties of samples were investigated by X-ray diffraction (XRD), transmission electron microscope , X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), Raman spectroscopy and vibrating sample magnetometer. XRD and XPS data confirmed the formation of a single phase wurtzite type ZnO structure for all the samples. PL measurements revealed that all the three samples had an UV emission and a defect emission, and the Ce ions doping induced a red shift in the UV emission and an increase in the defect emission. Zn_0.97Cr_0.03O and Zn_0.96Cr_0.03Ce_0.01O samples showed the obvious hysteresis loops at room temperature and the saturation magnetization (Ms) increases with incorporating of Ce.     

Effect of dopant concentration on the structural, electrical and optical properties of Mn-doped ZnO films

The Mn-doped ZnO (Zn_1 − xMn_xO) thin films with manganese compositions in the range of 0-8 at.% were deposited by radio-frequency (RF) magnetron sputtering on quartz glass substrates at room temperature (RT). The influence of Mn concentration on the structural, electrical and optical properties of Zn_1 − xMn_xO films has been investigated. X-ray diffraction (XRD) measurements reveal that all the films are single phase and have wurtzite structure with (002) c-axis orientation. The chemical states of Mn have been identified as the divalent state of Mn²⁺ ions in ZnO lattice. As the content of Mn increases, the c-lattice constant and the optical band gap of the films increase while the crystalline quality deteriorates gradually. Hall-effect measurements reveal that all the films are n-type and the conductivity of the films has a severe degradation with Mn content. It is also found that the intensity of RT photoluminescence spectra (PL) is suppressed and saturates with Mn doping.     

Structural,optical and magnetic characterization of Cu-doped ZnO nanoparticles synthesized using solid state reaction method

Polycrystalline undoped and Cu-doped Zinc oxide (Zn_0.98Cu_0.02O) nanocrystals were successfully synthesized by solid-state reaction method. The micro structural, optical and magnetic properties have been characterized using powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive analysis using X-rays (EDAX), UV–Visible spectroscopy, Photoluminescence, Vibrating sample magnetometer and Electron paramagnetic resonance spectroscopy. XRD pattern reveals that the samples possess hexagonal wurtzite structure of ZnO without any secondary phase after copper doping. Optical absorption analysis of the samples showed a red shift in absorption band edge with copper doping in ZnO. Photoluminescence spectra of the samples shows prominent peaks corresponding to near band edge UV emission and defect related green emission in the visible region at room temperature and their possible mechanism have also been discussed. Magnetic measurements using VSM showed that the nanocrystalline copper doped ZnO exhibits ferromagnetic behaviour at 300 K. EPR analysis also confirms the substitution of Zn site by Cu²⁺.     

Effects of Mn dopant on tuning carrier concentration in Mn doped ZnO nanoparticles synthesized by co-precipitation technique

Zn_1???x Mn _x O (x?=?0.002–0.01) nanoparticles were synthesized by co-precipitation method. The detailed crystal structure and compositional characterizations were characterized by the XRD patterns, Raman spectra, XPS, HRTEM and SEM. the XRD and XPS results show the Mn²⁺ ions are substitute for Zn²⁺ ions in the ZnO matrix. In the Raman spectra, the E₂(high) peak shifts to lower frequency and the higher intensity of A₁(LO) peak appears in the sample with increasing doping concentrations of Mn, indicating a higher concentration of donor defects are introduced in ZnO nanoparticles. Then, the carrier concentration induced by oxygen vacancies are analyzed from the optical absorption spectra. By analyzing the O1s XPS spectrum by Lorentz fitting and PL spectra by Gaussian fitting, the oxygen vacancy concentration increases with Mn doping concentration. The present results suggest that the doped Mn²⁺ ions play a significant role on enhancing the carrier concentration of ZnO materials.     

Structural aspects of changes induced in PbTe by doping with Mn, In and Ga

The paper presents the extended results of structural investigations of Pb_0.9Mn_0.1Te, and Pb_0.9Mn_0.1Te systems doped with In (2 at.%) and Ga (4 at.%) by means of EXAFS (extended X-ray absorption fine structure) technique. EXAFS measurements performed at Te–, Mn–, In– and Ga–K absorption edges at different temperatures are complemented with X-ray diffraction, flame absorption and X-ray fluorescence analysis. That way the complete information about elemental concentration; crystal structure; local environment around constitutive and impurity atoms (including their displacements from the regular lattice positions); local and long-range ordering; and the overall influence of doping on the host crystal structure is derived. The obtained results represent an important step towards understanding the structural aspects of doping of lead telluride-based semiconductors with Mn and group III elements and their connection to electronic and optical phenomena important for their applications.     

Structure and magnetic properties of (Co,Mn) co-doped ZnO diluted magnetic semiconductor nanoparticles

The ZnO, Zn_0.96Mn_0.04O, Zn_0.95Mn_0.04Co_0.01O, Zn_0.94Mn_0.04Co_0.02O and Zn_0.92Mn_0.04Co_0.04O nanoparticles were synthesized by simple chemical precipitation technique. The effects of co-doping on the structure and magnetic properties of these nanoparticles were studied. The X-rays diffraction (XRD) scans were performed in the 2θ range of 20°–80°. The XRD patterns, at 300 K, of all the pure and co-doped ZnO samples confirmed the formation of wurtzite-type structure. X-ray diffraction and transmission scanning electron microscope analysis indicated that the high spin Co²⁺ and Mn²⁺ ions were substituted for the Zn²⁺ ions at tetrahedral sites. The average size of the nanoparticles were increased from 17 to 24 nm with the increase of dopants concentration. Moreover, Energy Dispersive X-ray spectroscopy (EDX) confirmed the synthesis results. All Zn_0.96?xMn_0.04Co _x O (x?=?0.0, 0.1, 0.2 and 0.4) nanoparticles samples were observed to be paramagnetic below 300 K. However, a large increase in the magnetization was observed below 40 K. This behavior, along with the negative value of the Curie–Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicated the ferromagnetic nature of the samples. The origin of ferromagnetism is likely to be the intrinsic characteristics of the Co and Mn doped samples. The high magnetization was noted for the 1 wt% Co co-doped Mn–ZnO annealed samples as compared to other samples with Co concentration above and below this threshold concentration.     

Influence of Mn impurity on formation of secondary phases and optical properties of ZnO NPs

ZnO:Mn nanoparticles with various Mn concentrations (1–7%) were synthesized by a simple chemical method at low temperature. Structural and optical properties of as synthesized samples were investigated by X-ray diffraction (XRD), UV–vis absorbance, and photoluminescence (PL) spectrophotometers, respectively. XRD patterns of the ZnO:Mn nanocrystals indicate that in low Mn concentrations (1 and 3%), the ZnMn₂O₄ nanoparticles are formed, whereas in high Mn concentrations (5 and 7%), more Mn atoms replace Zn atoms in crystalline lattice, so that Mn₃O₄ is formed. It is also found that the size of the ZnO:Mn nanocrystals increases from 7.82 to 76.07?nm with increasing Mn concentration from 1 to 7%. Band gap energy of the samples, calculated by extrapolation of (αhν)² versus hν curves, shows a decrease in band gap with increasing the Mn concentration from 1 to 7%. The size of nanoparticles calculated by effective mass approximation model is nearly in accordance with the one calculated by Scherrer formula. The PL spectra of low Mn concentration ZnO:Mn nanoparticles indicate a weak green emission which vanishes in highly Mn concentrated ZnO:Mn samples.